The effect of glucose and ammonium sulfate on kinetic acidification by heterogeneous mixed culture

Summary The effect of glucose and ammonium sulfate concentration on the kinetics of lactic acid formation by a heterogeneous mixed culture was evaluated by the sole product formation using the Gompertz model, which can be used to define culture media composition taking into account product accumulation and acidification rate constant. A compromise between ionic inhibition and nitrogen limitation was found by using ammonium sulfate as nitrogen source. The sugar tolerance was similar to that in exenic cultures.     

Catalytic biotransformation of physiologically active 1-methyl-4- aryl-1,2,3,6-tetrahydropyridines under the action of monoaminooxidase

Kinetics of monoamine oxidase (MAO) catalyzed dehydrogenation of neurotropic analogues of biogenic monoamines in the 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine series were studied. It is shown that methyl substitution in the phenyl ring increases significantly the enzyme-substrate affinity, but the substituent's effect on the catalytic stage largely depends upon its position in the ring. o- and m-Methyl derivatives were preferably oxidized by B type of MAO, whereas p-total derivative was oxidized by B type as well as by A type of the enzyme. In the course of the oxidation reactions MAO is irreversibly inhibited by the dihydropyridinium product of the reaction, particularly in case of methyl derivatives. The significant and structure-dependent inhibition of the enzyme might be responsible for the differences in neurotropic properties of the above substrate homologues.     

Discrepancy in hormone binding and information transfer between sister cells of Tetrahymena clones

Tetrahymena cells treated with insulin in mass cultures were separated to single-cell clones or one of the "sister-cells" of dividing Tetrahymena (in single-cell culture) was treated with insulin. In both cases the FITC-insulin binding of sister-cells were compared. The insulin imprinting significantly increased the insulin binding of cells. There was also a significant difference between the imprinted and not imprinted sisters as well as between the not imprinted sisters. This demonstrates the existence of a difference (in hormone binding) between sister-cells and justifies that the information of the first hormone treatment (imprinting) is not equally divided between the sister-cells.     

Effect of procaine hydrochloride on the electrophoretic mobility of human red blood cells

The interaction of cationic anesthetics with biological membranes and the resulting alterations of membrane electrokinetic properties continue to be of current interest. The present study was designed to examine the effects of procaine hydrochloride (PRHCL) on the mobility of human red blood cells (RBC); electrophoretic measurements were made on RBC suspended in phosphate-buffered saline (PBS, pH = 5.0, 7.4, or 9.2), autologous plasma or 3 g% dextran T70/PBS (pH = 7.4), with PRHCL concentrations from 8 x 10(-6) to 8 x 10(-2) M. Low concentrations of PRHCL (8 x 10(-5)-8 x 10(-3) M) significantly (p less than 0.001) increased RBC mobility, with a maximal increase of 8.2% at 8 x 10(-4) M. Conversely, a higher PRHCL concentration (8 x 10(-2) M significantly (p less than 0.001) decreased RBC mobility. Both glutaraldehyde fixation and lipid extraction abolished any PRHCL-induced increase in RBC mobility; the observed increases in mobility for normal cells are, thus, consistent with a mechanism based on expansion of the RBC membrane glycocalyx. Microelectrophoretic methods were also used to study the effect of PRHCL (8 x 10(-4) and 8 x 10(-2) M) on RBC membrane calcium binding, with the results indicating that PRHCL competes with calcium for neuraminate binding sites. We conclude that the observed changes in RBC electrokinetic properties reflect incorporation of PRHCL into the RBC membrane; such changes may be of importance in modulating cell-cell interactions.     

Cooperative binding of primycin and gramicidin on erythrocyte membranes. A cation transport study

In this paper the authors present a comparative study of the actions of the antibiotics primycin and gramicidin on the erythrocyte membrane permeability. It has been found that both antibiotics have a nonlinear effect on the membrane permeability. Above a threshold antibiotic concentration, which is characteristic of the type of the antibiotic, the cation permeability of the erythrocyte membranes increases sharply. In the range of nonlinearity the transport-kinetic curves level off before achieving the equilibrium radioactive ion distribution between the extra- and intracellular spaces. A stochastic model of the cooperative and aspecific incorporation of antibiotic molecules into the membrane explains the experimental findings. The authors conclude that membrane permeability increases at the places where two or more antibiotic molecules form aggregates in the membrane.     

Two subunits of mannose permease, II-PMan and II-MMan, of Escherichia coli mediate coliphage N4 infection

Mutant strains of Escherichia coli that lack one or all of the intact components of mannose permease do not support the growth of phage N4. Complementation experiments using three recombinant plasmids containing DNA fragments coding for the subunits of mannose permease revealed that among the three component subunits, II-PMan and II-MMan alone are sufficient to confer N4 sensitivity.     

Functional alpha 2-adrenoceptors in rat adipocytes: inhibition of cyclic AMP accumulation

Alpha 2-adrenoceptor activation inhibits cyclic AMP accumulation in fat cells from many species. However, the presence of alpha 2-adrenoceptors in rat adipocytes has been difficult to demonstrate. We observed that alpha 2-adrenergic activation inhibits forskolin-stimulated cyclic AMP accumulation both in rat and hamster adipocytes; UK 14304, p-amino clonidine and clonidine were the agents with higher efficacy. The effect of UK 14304 was blocked by yohimbine but not by prazosin demonstrating the involvement of alpha 2-adrenoceptors. Pertussis toxin blocked the alpha 2-adrenergic effect. Our results demonstrate the presence in rat fat cells of alpha 2-adrenoceptors coupled to adenylate cyclase via "Gi".     

Home range use and the exploitation of gum in the marmosetCallithrix jacchus jacchus

Three wild groups of common marmoset, Callithrix jacchus jacchus,in north-east Brazil, of approximately similar size, had home ranges between 2.5 and 6.5 ha. But their core areas were similar in size between 1.0 and 1.5 ha, with a monthly area of heavy use between 1.1 and 1.6 ha. The groups were selective in the use of their home ranges, even though they were small: they used some areas heavily and others lightly. The core areas had higher densities of trees that produced gum exudates than did other parts of the home ranges. Our data suggest that a group of marmosets in this habitat may require a minimum of about 50 gum trees in its home range at a minimum density of about 50 trees/ha. In addition, the animals require suitable trees in which to sleep. We suggest that patches of forest with these desirable properties remain relatively fixed in size and location over the years and that individual animals are constantly in flux between them.     

Elevated VIP and endotoxin plasma levels in human gram-negative septic shock

Vasoactive intestinal polypeptide (VIP) and endotoxin (lipopolysaccharides, LPS) were measured in plasma samples from 11 patients with bacteriologically verified meningococcal disease. Five patients suffered fulminant septicaemia, developed severe septic shock, and 2 died due to circulatory collapse. Initially, all 5 had levels of VIP above 4 pM and plasma endotoxin above 200 ng/liter. Five patients were diagnosed as meningitis and 1 as having meningococcaemia, all with a normal circulatory state. None of these 6 patients had initially levels of VIP above 2.5 pM or endotoxin levels above 25 ng/liter (P less than 0.001). A correlation existed between plasma endotoxin and VIP levels (r = 0.735, P = 0.01). Sequentially collected samples from 3 patients showed rapidly declining VIP levels after initiation of antibiotic and fluid treatment. These results are in agreement with previous animal experiments, suggesting that endotoxin directly or indirectly stimulates the VIP-ergic nervous system in the initial phase of gram-negative septic shock in man.